I've got to have my A/C recharged and I'm wondering...what year was the refrigerant changed?

I'm not sure of the refrigerant types....which one is currently being used as aposed to which one has been discontinued....or which one I had.....but my 4Runner is a '93 and I had to empty all the refrigerant when I pulled my compressor off.

Will I be able to have it refilled or will I need to have my A/C system converted to accept the new refrigerant?

And if I have to have my A/C system converted, what is involved in converting it. Is it just the compressor...or is there more to it than that?